The issue occurred with one of six modules, so I deleted all but the offending module ('sick' module which cannot find classes in same package) - and the the issue was fixed. I then added the other modules back to the project one-by-one and found the the problem was related to a single module which had a reference to the 'sick' modules source path.

I found in another module this entry in .iml file

<orderEntry type="module-library">

      <library>

        <CLASSES>

          <root url="file://$MODULE_DIR$/lib/compile-no-deploy" />

        </CLASSES>

        <JAVADOC />

        <SOURCES>

         <root url="file://$MODULE_DIR$/../SICK_MODULE/src" /> <== this references the the SICK_MODULES source path

        </SOURCES>

        <jarDirectory url="file://$MODULE_DIR$/lib/compile-no-deploy" recursive="false" />

      </library>

    </orderEntry>

When I deleted this reference manually, the problem was fixed:

<orderEntry type="module-library">

      <library>

        <CLASSES>

          <root url="file://$MODULE_DIR$/lib/compile-no-deploy" />

        </CLASSES>

        <JAVADOC />

        <SOURCES />

        <jarDirectory url="file://$MODULE_DIR$/lib/compile-no-deploy" recursive="false" />

      </library>

    </orderEntry>

Denis,

   Raised incident IDEA-55557. The issue can be summarized as attaching the jar file source fin 'B' module to a dependency causes the "cannot find classes in same package issue" in the module 'A' whose source is referenced.

So:

1. module B uses module A jar file (both modules in same project)

2. Open module B dependencies dialog, attach sources to module A source dir

3. open module A in IDE and open a class in any package

4. note that other classes in same package are unresolved and shown as such

Serge